1. Field of the Invention
The present invention relates to an EGR pipe provided with a plurality of upper fins and lower fins.
2. Description of Related Art
Japanese Patent Application Publication No. 2011-111938 (JP 2011-111938 A), for example, describes a configuration in which part of exhaust gas discharged from a combustion chamber of an internal combustion engine is flowed back to an intake side of the combustion chamber.
In order to improve cooling performance, an EGR passage portion configured to flow back the exhaust gas is provided with a plurality of upper fins and lower fins having an increased heat exchange area with the exhaust gas. The upper fins and the lower fins are provided along an exhaust gas flow direction (a lengthwise direction of the EGR passage portion), and the plurality of upper fins and the plurality of lower fins are provided so as to face each other across a predetermined space in a direction (a width direction of the EGR passage portion) perpendicular to the lengthwise direction of the EGR passage portion. Further, since the upper fins and the lower fins are placed at positions where the upper fins correspond to the lower fins in the width direction of the EGR passage portion, the upper fins and the lower fins are provided so as to face each other across a predetermined space in a height direction of the EGR passage portion. Heights of the upper fins and the lower fins are set to be generally constant over a whole length of the EGR passage portion. The upper fins and the lower fins are narrowed in width toward their respective projection directions, so that both sides thereof in the width direction have inclined surfaces.